A number of compositions and methods have been developed to reduce the concentration of solvated compounds and ions from liquid water or environments containing liquid water. Such compositions and methods are desirable for use in water remediation applications including sewage or wastewater treatment; removal of leacheates such as excess fertilizers, pesticides, herbicides, or nematicides from groundwater sources, particularly where a high rate of percolation of such compounds is known; remediation of leacheates from e.g. landfill areas or industrial streams carrying toxins or other hazardous waste; desalinization of seawater; treatment of municipal water sources; and the like.
Many conventional water remediation compositions and methods are of limited use in one or more agricultural and industrial processes where such water remediation is needed. Limitations of conventional technologies include inability to maintain dimensional stability and integrity during use, compositional instability before or during use, foaming during processing or in use, water solubility (too hydrophilic) or insufficient wettability (too hydrophobic), high viscosity leading to difficulties in processing and/or use, pH sensitivity, and limited ranges of compounds that can be sorbed/retained by the composition due to inherent chemical incompatibilities. In some cases, the cost of a conventional technology is prohibitive.
Conventional technologies include microorganism-based or plant-based treatments; use of impermeable membranes to collect leacheates and runoff for subsequent treatment at a remote treatment/separation facility, oxidation lagoon, and the like; use of adsorbents such as activated carbon, silica, silicates, alumina, and synthetic zeolites and clays to capture compounds; solid phase extraction (affinity-based chromatographic techniques and materials) using compositions such as alkylated silicas or other functionalized silicas or functionalized clays, and the like; and combinations of these technologies.
Water holding enhancement and ion exchange capacities in a water remediation composition are also beneficial but are generally lacking in the conventional methods and compositions. For example, superabsorbent polymers (SAP) are useful for water retention in soil, for example, but due to their hydrophilic or even hygroscopic nature they are not typically useful for removal of organic compounds from a remediation environment. Further, as most SAP rely on ionic groups such as polyacrylate salts to provide the hygroscopic character of the polymers, the presence of ionic content in the water reduces the ability of the SAP to swell and retain water as compared to the same SAP in a substantially ion-free environment.
The conventional technologies for water remediation and water retention are not generally suitable for carrying out the slow and/or controlled release of organic compounds. Such release is advantageously employed for e.g. fertilizers, pesticides, herbicides, or nematicides, wherein the composition is “preloaded” with a compound, then the preloaded composition is applied to soil for release of the compound. Slow release compositions are highly desirable in agricultural applications for preventing leaching out or runoff of the chemicals, where such compositions are capable of release of one or more chemicals of interest at a targeted rate. The targeted rate, for example, can be commensurate with the rate of absorption by a particular plant or group of plants. In such cases, the affinity of the composition for the compound to be released is key to its release properties. However, most conventional technologies such as those listed above are simply not useful or practicable for such “reverse” uses as slow and/or controlled release of chemicals into a selected environment.
One material that is suitable for both water remediation and slow release of compounds in agricultural applications is described by Elliott, U.S. Pat. No. 6,811,703 (“Elliott”). Elliott teaches compositions and methods related to the reaction of a methylolated dialkyl diphenol with a monoalkyl ether adduct of a polyalkylene oxide bromide to yield a polyalkylene oxide adduct of the methylolated dialkyl diphenol, or polyoxyetheralkyldiphenol. The adduct is then employed in a reaction with a phenolic aldehyde prepolymer either in an aqueous environment or on a solid support, relying on the methylol moieties of the adduct to achieve the reaction with the phenolic aldehyde prepolymer. The compositions can be used directly, or sprayed and cured on a particulate solid support, for water remediation. Once applied to the remediation environment, the crosslinked network polymer is effective at reducing and retaining a plethora of organic compounds. Additionally, the crosslinked composition adheres to ion exchange compositions such as clays, enabling scavenging of ionic entities from the remediation environment.
Once the phenolic aldehyde is mixed with the adduct, the crosslinking reaction takes place at commonly employed storage temperatures (e.g. between 0° C. and 30° C.) leading to a limited shelf life. Because of this reactivity, application of the composition to the remediation environment, or spraying the composition onto the surface of a particulate, must be carried out within a few days of mixing the adduct with the prepolymer.
Additionally, a preferred diphenol starting material in the compositions of Elliott is bisphenol A (4-[2-(4-hydroxyphenyl)propan-2-yl]phenol), a suspected xenoestrogen that has been associated medically with organizational changes in the prostate, breast, testis, mammary glands, body size, brain structure and chemistry, and behavior of laboratory animals. Where bisphenol A is employed, it is methylolated by reacting the bisphenol with formaldehyde, a known carcinogen. Both bisphenol A and formaldehyde are considered undesirable compounds in the industry and thus suitable replacements or alternative materials are actively sought.
Smith et al., U.S. Pat. No. 3,857,815 (“Smith”) teaches a polypropylene glycol or polybutylene glycol modified phenolic aldehyde resole. Resoles are phenol formaldehyde resins having a ratio of formaldehyde to phenol of at least 1 and typically about 1.5. The materials of Smith are formed by blending a phenolic aldehyde with polyalkylene glycol plus aniline or m-hydroxyaniline, then curing with excess formaldehyde. There is no evidence that the polyalkylene glycol undergoes any reaction with the resole, nor would one of skill expect any reaction between the hydroxyl-terminated alkylene glycol and the resole to occur under the conditions set forth by Smith. Rather, it would appear that the polylkylene glycol is merely an additive that, depending on molecular weight, becomes entangled or entrapped within the resole, analogous to a semi-interpenetrating network. Such formulations are unsuitable for use in water remediation applications. The remediation environment would cause the polyalkylene glycol to leach out of the crosslinked resole network. Such leaching provides instability during use in a water containing environment.
There is a need for water remediation compositions that are environmentally benign; do not require the use of bisphenol A or excess formaldehyde; are effective for retention of a wide variety of organic compounds, ionic content, or both in environments containing liquid water; are storage stable in a convenient form, from which the final product can be easily prepared; have water retention properties; are stable in their intended use environment; and can be used for their slow release or controlled release properties, for example in timed release of chemicals commonly employed in agriculture.